1. Field of the Invention
This invention relates to a new and improved protective guard for inner tubes of relatively narrow tires such as bicycle tires. In particular, this invention relates to a novel liner insertable between an outer tire casing and an air-filled inner tube of a tire for protecting the inner tube against punctures and for preventing cracking of the tire casing wall.
2. Description of the Prior Art
The sport of bicycling in the United States is presently undergoing a rejuvenation. This sudden increase in the use of bicycles has put pressure on the industry to produce larger numbers of bicycles and on the tire industry to produce larger numbers of tires to meet the increased demand. However, because of high per unit manufacturing cost and low per unit profit, the bicycle tire industry has not kept pace with the increased demand and has not endeavored to transfer recent innovations and developments in automobile tires to bicycle tires.
There are significant differences between automobile tires and bicycle tires. Consequently many of the innovations and developments of the former can not be incorporated in the latter. In addition, bicycle tires are confronted with different hazards and different degrees of hazards than are automobile tires. Bicycle tires usually are comprised of a narrow outer rubber casing having a thin cross-section and an inner air-filled inner tube; whereas most modern automobile tires are comprised of a single wide tubeless outer casing having a thick cross-section and reinforcing fibers imbedded therein. A simple puncture of a bicycle tire, for example by a nail, will usually render the tire unusable, but this simple puncture in an automobile tire probably will have no effect on the tire because of its puncture sealing capabilities.
The hazard with which a tire is confronted is determined primarily by the use of the tire. Because a bicycle travels at much lower speeds than an automobile, the bicycle is usually restricted to travelling along the edges of streets where the tires are subjected to puncture causing debris such as broken glass, rocks, and nails. Bicycles frequently also are taken along unpaved and usually unimproved routes which subject the tires to unusual stresses. Because bicycles do not have shock mounted wheels, the tires must absorb the full effects of any rough treatment. Should the tires be underinflated, the rough treatment will cause significant compression of the tires and abnormal flexing of the side walls of the tire casing and eventual cracking of the side wall.
However, instead of being equipped with thicker and stronger tires so that the tires can withstand the unusual stresses, bicycles are equipped with relatively narrow tires comprised of a very thin outer casing and an air-inflated inner tube. Consequently a large numbr of bicycles are being disabled by worn and punctured tires and a need exists for bicycle tires which are more resistant to damage and which last longer.
Before automobiles were equipped with their present self-sealing, tubless, steel-belted tires, similar problems occurred in the automotive industry. A number of armored tire interliners were developed to attempt to protect the inner tube against punctures. Usually, however, such interliners caused more problems than they solved. Many of the prior art devices had overlapping ends or separable joints which usually pinched and ruptured the inner tube when the tire was deformed by a bump or the walls of a hole. These interliners also would move relative to the inner tube and the tire casing thereby pinching or wearing away the inner tube. Furthermore, the interliners were relatively thick and heavy, and were designed to be used with tires having thick outer tire casings. In any event, the prior art interliners can not be fabricated in the narrow widths, and light weights thus providing the degrees of flexibility needed by bicycle tires. Hence, the prior art interliners are not adaptable to bicycle tires. In addition, the prior art interliners are expensive to fabricate and difficult to properly install.